B.U.V

BAITED UNDERWATER VIDEO

Ever wondered how scientists count fish?
One method that is used widely around New Zealand and the world is Baited Underwater Video (BUV).
This method uses bait to attract fish in front of a camera. Researchers can then count the fish on the video to get an idea of species abundance and diversity.

HOW IT WORKS

BUV equipment comes in a variety of shapes and sizes. Our example uses a very similar setup of equipment and process as that used by the Department of Conservation (DOC).

HOW IT LOOKS

The BUV we use has a metal frame that holds a camera overlooking a bait pot. On the lower arm of the frame, there are black marks which give the observer an idea of how big the fish are. Each mark is 10cm long.

The top of the frame is tied to two floats. One of the floats is underwater with the frame and helps to keep the frame upright. The other float is on the surface and is to help the boat find the camera again when the trial is over.

HOW IT RUNS

To run a BUV trial, researchers lower the frame over the side of the boat. When the frame touches the seafloor the trial begins. We run our BUV trials for 30 minutes. Once the time is up, you pull the BUV back to the surface and download the video footage for analysis. 
When researchers do a BUV survey of an area, they will repeat this process over and over in different locations. The more replications (or trials) you do, the more confident you can be that your results are accurate.

HOW IT RUNS

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Q&A ROUND 1!

Q. Why do you think some researchers use remote cameras instead of having SCUBA divers count fish in an area?
Q: Do you think this method can be used to investigate all fish?

Or is it limited to certain types of fish?
 Q. What are two things that you would want to keep the same during every trial of a BUV survey?

BLUE COD

Pākirikiri, Rāwaru       Parapercis colias

For our BUV's, we're analysing the number of Blue Cod!
Why Blue Cod you ask? Well, firstly they're endemic to New Zealand and inhibit open reef areas or sand and gravel near patch reefs... it's also one of the most common caught recreational fish in South Taranaki, and our fishing survey's indicated Project Reef as a possible Blue Cod nursery!

3 COLOUR PHASES

Scroll over each image to discover the three colour phases of Blue Cod! 
A big thank you to Dr Malcom Francis who's wonderful book 'Coastal Fishes of New Zealand' contains the following images of & information on Blue Cod! 
Coastal Fishes of New Zealand  has been Project Reef's 'go to' book for identification, biology & behaviour for fish!

TRY IT YOURSELF!

When we watch BUV footage, there is no way of knowing if the fish that swims in during the first minute is different from a similar-looking fish that swims in 5 minutes later. We don’t want to be counting the same fish twice! To avoid this, we take the one frame of the video that has the most fish in it and use that as our count for that trial.

You can try doing this for the video below. Try pausing the video every 30 seconds and counting the number of blue cod. You could even pause it every 10 seconds if you wanted to be more accurate!

LET'S GET TO WORK!

Ever wondered how scientists count fish? One method that is used widely around New Zealand and the world is Baited Underwater Video (BUV).This method uses bait to attract fish in front of a camera. Researchers can then count the fish on the video to get an idea of species abundance and diversity.

ADDITIONAL SPECIES

SNAPPER

Snapper eat virtually any animal matter, and diet changes with size.

OCTOPUS

One of the largest carnivores on the reef is the octopus!

SEVEN GILL SHARK

These sharks investigate objects by bumping them with their snouts.

SCARLET WRASSE

These fish have three colour phases... juvenile, female and male.

CARPET SHARK

These sharks are nocturnal, usually sluggish & are not dangerous.

Q&A ROUND 2!

Q. Why do we want to avoid counting the same fish twice?
Q. Could there be problems with multiple people analysing different videos in a BUV survey?
Q. Why do we want to measure the fish using the marks on the frame?

MORE BUV RESOURCES

BUV &
Hagfish slime!

Hagfishes (Myxinidae) are a family of jawless marine pre-vertebrates. Using baited remote underwater video systems, it was revealed that hagfishes are able to choke their would-be predators with gill-clogging slime! Find out more about
the work of Vincent Zintzen, Clive D. Roberts, Marti J. Anderson, Andrew L. Stewart, Carl D. Struthers & Euan S. Harvey's work on Hagfish predatory behaviour and slime defence mechanism!

Project Reef Life

Get curious, discover & learn about life 11km offshore of South Taranaki New Zealand,  23m deep.

Phone: 027-205-9673

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